Mega Beasts9/8c DiscoveryThis new series brings to life some of the most ferocious dinosaurs to roam the earth. Scientists piece together what these mysterious creatures looked like, how they behaved, and what they encountered. In tonight's episode,… Read more

The Mega Beast Megalania seems like science fiction--an 18-foot lizard with a mouthful of dagger teeth and venom, but it was in fact the biggest reptilian predator since T. Rex. Some say they still survive in the Outback of Australia.

Acrocanthosaurus was a prehistoric weapon of mass destruction that lived 50 million years before T Rex. Loaded with the most powerful arms in dinosaur history, a scissor-like bite, and a hi-tech neck brace, this beast could kill prey ten times its size.

Meet Spinosaurus -- a carnivore twice the size of T Rex with a six-foot-high sail, long crocodilian skull, and massive claws. It may have been king of the dinosaurs 100 million years ago, but it wasn't without rivals, including prehistoric alligators.

With six foot jaws and a nasty disposition, the Mosasaur dined on giant sharks and plesiosaurs. An extra set of teeth on the roof of its mouth guaranteed that when it sunk its teeth into something, there was only one way out...down its gullet.